some mem layout tuning

3 files changed, 96 insertions, 0 deletions

diff --git a/debian/patches/0001-vm-make-struct-vm_map-fit-into-a-cache-line.patch b/debian/patches/0001-vm-make-struct-vm_map-fit-into-a-cache-line.patch
new file mode 100644
index 0000000..41a3ca4
--- /dev/null
+++ b/debian/patches/0001-vm-make-struct-vm_map-fit-into-a-cache-line.patch
@@ -0,0 +1,36 @@
+From 02f3fe277a80a4f32ffae04b061808a8bdf5bd59 Mon Sep 17 00:00:00 2001
+From: Justus Winter <4winter@informatik.uni-hamburg.de>
+Date: Wed, 30 Apr 2014 15:23:36 +0200
+Subject: [PATCH 1/2] vm: make struct vm_map fit into a cache line
+
+Currently, the size of struct vm_map is 68 bytes.  By using a bit
+field for the boolean flags, it can be made fit into a cache line.
+
+* vm/vm_map.h (struct vm_map): Use a bit field for the boolean flags
+wait_for_space and wiring_required.
+---
+ vm/vm_map.h | 7 +++++--
+ 1 file changed, 5 insertions(+), 2 deletions(-)
+
+diff --git a/vm/vm_map.h b/vm/vm_map.h
+index b6bc177..b8103eb 100644
+--- a/vm/vm_map.h
++++ b/vm/vm_map.h
+@@ -175,9 +175,12 @@ struct vm_map {
+ 	vm_map_entry_t		hint;		/* hint for quick lookups */
+ 	decl_simple_lock_data(,	hint_lock)	/* lock for hint storage */
+ 	vm_map_entry_t		first_free;	/* First free space hint */
+-	boolean_t		wait_for_space;	/* Should callers wait
++
++	/* Flags */
++	unsigned int	wait_for_space:1,	/* Should callers wait
+ 						   for space? */
+-	boolean_t		wiring_required;/* All memory wired? */
++	/* boolean_t */ wiring_required:1;	/* All memory wired? */
++
+ 	unsigned int		timestamp;	/* Version number */
+ };
+ 
+-- 
+1.9.2
+
diff --git a/debian/patches/0002-Add-some-padding-to-make-objects-fit-a-single-cache-.patch b/debian/patches/0002-Add-some-padding-to-make-objects-fit-a-single-cache-.patch
new file mode 100644
index 0000000..f2de691
--- /dev/null
+++ b/debian/patches/0002-Add-some-padding-to-make-objects-fit-a-single-cache-.patch
@@ -0,0 +1,58 @@
+From 065a76b5dfc8e495b6ed170df57a1ce86894ead0 Mon Sep 17 00:00:00 2001
+From: Justus Winter <4winter@informatik.uni-hamburg.de>
+Date: Wed, 30 Apr 2014 16:15:34 +0200
+Subject: [PATCH 2/2] Add some padding to make objects fit a single cache line
+
+Add four bytes of padding to struct ipc_space, struct vm_fault_state,
+and struct vm_map_entry.
+
+XXX vm_map_entry one is kinda expensive
+
+* ipc/ipc_space.h (struct ipc_space): Add four bytes of padding.
+* vm/vm_fault.c (struct vm_fault_state): Likewise.
+* vm/vm_map.h (struct vm_map_entry): Likewise.
+---
+ ipc/ipc_space.h | 1 +
+ vm/vm_fault.c   | 1 +
+ vm/vm_map.h     | 1 +
+ 3 files changed, 3 insertions(+)
+
+diff --git a/ipc/ipc_space.h b/ipc/ipc_space.h
+index c4683d2..278b4c9 100644
+--- a/ipc/ipc_space.h
++++ b/ipc/ipc_space.h
+@@ -79,6 +79,7 @@ struct ipc_space {
+ 	ipc_entry_num_t is_tree_total;	/* number of entries in the tree */
+ 	ipc_entry_num_t is_tree_small;	/* # of small entries in the tree */
+ 	ipc_entry_num_t is_tree_hash;	/* # of hashed entries in the tree */
++	char padding[4];		/* pad to cacheline size */
+ };
+ 
+ #define	IS_NULL			((ipc_space_t) 0)
+diff --git a/vm/vm_fault.c b/vm/vm_fault.c
+index 686156c..431480e 100644
+--- a/vm/vm_fault.c
++++ b/vm/vm_fault.c
+@@ -82,6 +82,7 @@ typedef struct vm_fault_state {
+ 	vm_offset_t vmfp_offset;
+ 	struct vm_page *vmfp_first_m;
+ 	vm_prot_t vmfp_access;
++	char padding[4];	/* pad to cacheline size */
+ } vm_fault_state_t;
+ 
+ struct kmem_cache	vm_fault_state_cache;
+diff --git a/vm/vm_map.h b/vm/vm_map.h
+index b8103eb..ac5f109 100644
+--- a/vm/vm_map.h
++++ b/vm/vm_map.h
+@@ -126,6 +126,7 @@ struct vm_map_entry {
+            -1 for non-persistent kernel map projected buffer entry;
+            pointer to corresponding kernel map entry for user map
+            projected buffer entry */
++	char			padding[4];	/* pad to cacheline size */
+ };
+ 
+ typedef struct vm_map_entry	*vm_map_entry_t;
+-- 
+1.9.2
+
diff --git a/debian/patches/series b/debian/patches/series
index 9825c75..e5010ab 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -5,3 +5,5 @@
 70_dde.patch
 
 protected_payload.patch
+0001-vm-make-struct-vm_map-fit-into-a-cache-line.patch
+0002-Add-some-padding-to-make-objects-fit-a-single-cache-.patch